Must agree with WWW, I did my PPL in USA and passed first time in 3 weeks, on hindsight I would have done it in the UK, the cracks certainly do appear as you progress to higher ratings. I wouldn't say the RT and airspace are vastly different, never really had a problem switching between US and UK RT having done some hours over there, although I did ask Leuchars for Flight Following once and was granted a Flight Information service by the amused controller.
I don't think it is actually the instruction that is bad in the US its the timescale, no time to consolidate on your morning lesson until you are back up for your afternoon lesson then again for your evening lesson. So you have virtually forgotten what went on in the morning. I know when it comes to advanced ratings this ability to learn quickly is needed but when learning the foundations a bit more time is needed. Don't think I could trim properly or fly straight and level when I got back from the States, and my hour building with a bad technique compounded the issues.
If I had to do it again I'd do it at a local club, at weekends and at night after work if possible, 2 lessons a weekish, would give plenty of time to reflect on each lesson. Also saves you taking time off work and all the other added expenses it costs going to the states.